Säteilyturvakeskus (STUK)

STUK has granted permission to start the OL3 reactor


The criticality and low power test permission granted today to Teollisuuden Voima Oyj (TVO) by the Radiation and Nuclear Safety Authority (STUK) means that the company can start the nuclear reaction in the Olkiluoto 3 reactor (OL3) for the first time.

In the permission, STUK states that the preconditions for criticality and low power tests are met and the commissioning tests performed before the first criticality show that the plant operates as planned. The commissioning tests also include re-tests carried out after the modifications.

Before the reactor is made critical, STUK will verify the start-up preparedness of the plant. In this context, STUK will check that the open issues presented in the criticality and low power test permission decision are in order.

STUK will monitor the reactor's start-up and low power tests on site in Olkiluoto. TVO is gradually increasing the power of the reactor. TVO needs STUK's permission to increase the power by more than 5% of the reactor's full power as well as to increase the power by more than 30% and 60%.

Experience and certainty from the hot functional tests

TVO started loading fuel to OL3 at March. STUK observed the start and progress of the loading in Olkiluoto. STUK also reviewed the plans and instructions concerning the hot functional tests following the loading and observed the most significant tests in Olkiluoto.

During the hot functional tests, TVO was able to verify that the dampers added to the pressuriser surge line have sufficiently reduced the problematic vibration of the line.

Project Manager Essi Vanhanen from the Radiation and Nuclear Safety Authority says that the commissioning phase has been a learning lesson for all the parties involved.

TVO investigated the exceptional events encountered during the commissioning tests and carried out investigations into the most significant incidents. STUK monitored the progress of the commissioning tests, the resolution of problems and checked the most significant modification work plans as well as carried out the necessary inspections in the repaired and modified sites.

Link: Supervision from fuel loading to the beginning of criticality

Further information:

Project Manager Essi Vanhanen, tel. +358 9 7598 8242



Project Manager Essi Vanhanen, tel. +358 9 7598 8242


About Säteilyturvakeskus (STUK)

Säteilyturvakeskus (STUK)
Säteilyturvakeskus (STUK)
Laippatie 4

Mediapalvelu: 010 850 4761http://www.stuk.fi

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